1. Field of the Invention
The invention relates generally to integrated circuit test connectors and more particularly to a coaxial surface mating connector wherein the impedance of the coaxial cable is maintained to and through the point of surface contact, and electrical interference between adjacent connectors is substantially eliminated.
2. Description of the Prior Art
The practice of testing electrical characteristics of miniature electronic devices, e.g. semiconductor components, integrated circuits, components, circuits, etc., is of prime importance to the electronic device manufacturer so as to discover the performance capabilities of devices prior to and after assembly. For example, in the semiconductor industry, it is desirable to test semiconductor devices while in wafer or slice form so as to eliminate unsatisfactory components prior to assembly. The manufacturer further tests the devices after final assembly and prior to shipment for quality assurance. The end users of the devices commonly test the devices prior to installation in the equipment of which the device has become a part. Increasing demand for miniature electronic devices further dictates that there be continuing emphasis placed on the electronic industry to provide equipment capable of performing these tasks at higher rates of speed with precise accuracy.
BNC connectors have provided one means for making the connection between a coaxial cable and electronic devices. However, when it becomes desirable to make a multiplicity of connections and each such connection requires a matched impedance environment within a relatively small area, BNC connectors become impractical due to their size and the fact that they must be connected individually by twisting each connector.
Test signals can be transmitted to the various devices to be tested by using what is known in the semiconductor industry as a probe head adapter. Such a device is described in the U.S. Pat. No. 3,866,119. In that patent the "pogo pin assembly" is used to transmit test signals from a test device to a terminal pad which is electrically connected to test probes which are in physical and electrical contact with the device to be tested. While such a system is satisfactory under some conditions, the higher frequencies of test signals currently in use causes problems which deteriorate the test signal.
As the frequency of test signals increases, the problem of impedance mismatches between the test signal cable and the terminal pad rises to significant proportions. The results are signal reflections which are now considered noise. The impedance mismatch problems occur in connections which transition between the transmission cable and the socket. The present art has not been able to maintain a matched impedance environment from the cable, through the connector and contact pin down to the surface contact of the terminal pad. Currently, connectors which require high insertion forces or are unshielded are used. The high forces can damage or misalign the delicate components with which they are used, especially when large numbers are ganged together.
Another problem with the prior art is that open lines i.e., unshielded, on the distal end of the contact pin open the system to outside noise and cross-talk between adjacent conductors which interferes with and deteriorates the test signals being sent and received.
Additionally, surface contamination can prevent proper electrical contact in present technology even when physical contact exists between the mating surfaces of existing systems.